Turning light pipe for a pupil expansion system and method

ABSTRACT

A display system includes a light pipe including elongated surfaces. The light pipe is configured to expand the image in a first direction through one of the elongated surfaces. The display also includes a waveguide including an output grating, a first surface, a second surface, and a side surface. The first surface and the second surface have a larger area than the side surface, the output grating being configured to provide the image expanded in a second direction. The second direction is different than the first direction. The image enters the waveguide from the one of the elongated surfaces.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/715,332, filed May 18, 2015, incorporated herein byreference in its entirety. The present disclosure is related to U.S.patent application Ser. No. 14/497,280, filed Sep. 25, 2014; U.S. patentapplication Ser. No. 14/465,763 filed on Aug. 21, 2014, which claims thebenefit of and priority to and is a Continuation of U.S. patentapplication Ser. No. 13/355,360, filed on Jan. 20, 2012 (now U.S. Pat.No. 8,817,350, issued on Aug. 26, 2014), which claims the benefit of andpriority to and is a Continuation of U.S. patent application Ser. No.12/571,262 filed on Sep. 30, 2009 (now U.S. Pat. No. 8,233,204, issuedon Jul. 31, 2012); U.S. patent application Ser. No. 13/869,866 filed onApr. 24, 2013, which claims the benefit of and priority to U.S.Provisional Patent Application No. 61/687,436 filed on Apr. 25, 2012,and U.S. Provisional Patent Application No. 61/689/907 filed on Jun. 15,2012; and U.S. patent application Ser. No. 13/844,456 filed on Mar. 15,2013, which claims the benefit of and priority to U.S. ProvisionalPatent Application No. 61/796,632 filed on Nov. 16, 2012, and U.S.Provisional Patent Application No. 61/849,853 filed on Feb. 4, 2013, allof which incorporated herein by reference in their entireties.

The present disclosure is also related to: U.S. patent application Ser.No. 13/251,087, filed on Sep. 30, 2011; U.S. patent application Ser. No.13/250,940 filed on Sep. 30, 2011, incorporated herein by reference, andassigned to the assignee of the present application; U.S. patentapplication Ser. No. 13/250,858 filed on Sep. 30, 2011, incorporatedherein by reference in its entirety, and assigned to the assignee of thepresent application; U.S. patent application Ser. No. 13/250,970 filedon Sep. 30, 2011, incorporated herein by reference in its entirety, andassigned to the assignee of the present application; U.S. patentapplication Ser. No. 13/250,994 filed on Sep. 30, 2011, incorporatedherein by reference in its entirety, and assigned to the assignee of thepresent application; and U.S. patent application Ser. No. 13/250,621,filed on Sep. 30, 2011, incorporated herein by reference herein in itsentirety and assigned to the assignee of the present application.

BACKGROUND

The present disclosure relates to substrate guided displays includingbut not limited to head up displays (HUDs), helmet mounted displays(HMDs), wearable displays, near eye displays, head down displays (HDDs),etc.

Substrate guided displays have been proposed which use waveguidetechnology with diffraction gratings to preserve eye box size whilereducing lens size. U.S. Pat. No. 4,309,070 issued to St. Leger Searleand U.S. Pat. No. 4,711,512 issued to Upatnieks disclose head updisplays including a waveguide where the pupil of a collimating opticalsystem is effectively expanded by the waveguide. The U.S. patentapplications listed in the Cross Reference to Related Applications abovedisclose compact head up displays (HUDS) and near eye displays usingmultiple gratings, multiple waveguides, and/or multiple waveguide layersfor pupil expansion.

Pupil expansion using multiple layers or multiple waveguides with inputand output diffraction gratings adds to the complexity of the waveguidedisplay. For example, pupil expansion using multiple layers, multiplewaveguides, and/or multiple gratings can add to the size, weight andcost of the display and can reduce the brightness and contrast of thedisplay. Further, expanding the pupil from a small round collimatinglens in two directions using two or more waveguides or using three ormore gratings to produce a final expanded pupil can be lossy due to airgaps and the number of gratings. The air gaps can induce geometriccoupling losses. Further, expanding the pupil from a small roundcollimating lens in two directions using two or more waveguides or usingthree or more gratings to produce a final expanded pupil can add haze tothe final image.

Therefore, there is a need for a display with reduced complexity, size,cost, and weight. There is further a need for a compact wearable displaythat uses diffraction gratings and is not susceptible to haze. Further,there is a need for a compact HUD which uses collimating opticsoptimized for constrained spaces associated with smaller aircraft. Yetfurther still, there is also a need for a small volume, lightweight,lower cost waveguide display with less lossiness and haze. Yet further,there is a need for a substrate waveguide near eye display or HUD thatrequires fewer gratings for pupil expansion. Yet further, there is aneed for a wearable display or HMD that requires fewer gratings forpupil expansion. Yet further, there is a need to mitigate solar flareeffects associated with waveguide displays.

SUMMARY

In one aspect, the inventive concepts disclosed herein are directed to anear eye optical display. The near eye display includes a light pipeincluding elongated surfaces. The light pipe is configured to expand animage in a first direction through one of the elongated surfaces. Thenear eye display also includes a waveguide including an output grating,a first surface, a second surface, and a side surface. The first surfaceand the second surface have a larger area than the side surface, and theoutput grating is configured to provide the image expanded in a seconddirection. The second direction is different than the first direction.The image enters the waveguide from the one of the elongated surfaces atthe side surface.

In one aspect, the inventive concepts disclosed herein are directed to amethod of displaying information. The method includes receiving light ina light pipe, receiving the light in a waveguide having a first surfaceand a second surface, and providing the light to an output grating viatotal internal reflection between the first surface and the secondsurface. The method also includes providing the light from the waveguidevia the output grating, where the light is provided with dual axis pupilexpansion with respect to the light received in the light pipe.

In one aspect, the inventive concepts disclosed herein are directed toan apparatus for providing an image. The apparatus includes a light pipeand a waveguide comprising an input surface and an output surface. Theinput surface is non-planar with respect to the output surface. Lightfrom the non-gradient or gradient reflective coating is received at theinput surface, and the light is ejected from the output surface of thewaveguide by an output grating.

BRIEF DESCRIPTION OF THE DRAWINGS

The exemplary embodiments will become more fully understood from thefollowing detailed description, taken in conjunction with theaccompanying drawings, wherein like reference numerals refer to likeelements, in which:

FIG. 1 is a general block diagram of a display system according to someexemplary embodiments;

FIG. 2A is a perspective view schematic drawing of a display system wornby a user according to some exemplary embodiments;

FIG. 2B is a more detailed perspective view schematic drawing of thedisplay system illustrated in FIG. 2A without showing the user accordingto some exemplary embodiments;

FIG. 2C is a planar front view schematic drawing of the display systemillustrated in FIG. 2B according to some exemplary embodiments;

FIG. 3 is planar side view schematic drawing of a light pipe for thedisplay system illustrated in FIG. 2A according to some exemplaryembodiments;

FIG. 4 is a planar top view schematic drawing of the light pipeillustrated in FIG. 3 according to some exemplary embodiments;

FIG. 5 is a perspective view schematic drawing of the of the light pipeillustrated in FIG. 3 according to some exemplary embodiments;

FIG. 6 is planar front view schematic drawing of the light pipe and thewaveguide for the display system illustrated in FIG. 2 according to someexemplary embodiments;

FIG. 7 is a graph showing reflectance versus thickness at a number ofangles for a gradient reflection coating associated with the light pipeillustrated in FIG. 3 according to some exemplary embodiments;

FIG. 8 is a graph showing reflectance and light output versus number ofbounces for a gradient reflection coating associated with the light pipeillustrated in FIG. 3 according to some exemplary embodiments;

FIG. 9 is a planar side view schematic drawing of a projector and alight pipe and waveguide assembly at a first orientation for the displaysystem illustrated in FIG. 1 according to some exemplary embodiments;

FIG. 10 is a planar back view schematic drawing of the projector and thelight pipe and waveguide assembly at the first orientation illustratedin FIG. 9 according to some exemplary embodiments;

FIG. 11 is a planar side view schematic drawing of a projector and alight pipe and waveguide assembly at a second orientation for thedisplay system illustrated in FIG. 1 according to some exemplaryembodiments;

FIG. 12 is a planar back view schematic drawing of the projector and thelight pipe and waveguide assembly at the second orientation illustratedin FIG. 11 according to some exemplary embodiments;

FIG. 13 is a planar side view schematic drawing of a projector and alight pipe and waveguide assembly at a third orientation for the displaysystem illustrated in FIG. 1 according to some exemplary embodiments;and

FIG. 14 is a planar side back schematic drawing of the projector and thelight pipe and waveguide assembly at the third orientation illustratedin FIG. 13 according to some exemplary embodiments.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Following below are more detailed descriptions of various conceptsrelated to, and embodiments of, an optical display and methods ofdisplaying information. The display system and method can be implementedin any of numerous ways, as the disclosed concepts are not limited toany particular manner of implementation. Examples of specificimplementations and applications are provided primarily for illustrativepurposes.

Exemplary embodiments will now be further described by way of examplewith reference to the accompanying drawings. It will be apparent tothose skilled in the art that the some embodiments may be practiced withnone, one, some or all of the features and advantages as disclosed inthe following description. For the purposes of explaining aspects theinvention, well-known features of optical technology known to thoseskilled in the art of optical design and visual displays have beenomitted or simplified in order not to obscure the basic principles ofsome embodiments. In the following description, the terms light, ray,beam and direction may be used interchangeably and in association witheach other to indicate the direction of propagation of light energyalong rectilinear trajectories. Parts of the following description willbe presented using terminology commonly employed by those skilled in theart of optical design.

Referring generally to the Figures, systems and methods relating tonear-eye display systems, HUD systems, worn display systems, HMDsystems, and HDD systems are shown according to various embodiments. Thedisplay system of some embodiments advantageously provides dual axisexpansion with less reduction in brightness and contrast as well as lesssusceptibility to haze. The display system advantageously can beutilized in HMDs or head mounted/worn displays, near eye displays, andHUDs for many applications, including but not limited to militaryapplications, aviation applications, medical applications, entertainmentapplications, simulation applications, vehicle applications and consumerapplications (e.g., augmented reality glasses, etc.) in someembodiments. The display system uses a light pipe to increase the pupilin one direction and a waveguide with a grating to increase the pupil inanother direction in some embodiments. Using the systems and methodsdisclosed herein, a highly integrated, low cost, light weight, displaysystem can be provided which is less susceptible to solar flare effects,brightness, contrast, and haze issues according to some embodiments.

With reference to FIG. 1, a display system 100 can be embodied as a HUD,an HMD, a near-eye display, a worn display, HDD, etc. Display system 100includes a projector 102, a light pipe 104, and a waveguide 106.Waveguide 106 includes an output coupler or grating 108. Display system100 provides light in the form of an image into light pipe 104. In someembodiments, light pipe 104 has an input coupler or grating that isresponsible for turning the light from projector 102 down light pipe 104for expansion. Light pipe 104 expands the image in one direction (e.g.from right to left in FIG. 1) and provides the image into waveguide 106(e.g., via a leaky transmissive coating) in some embodiments. Lighttravels partially by total internal reflection in waveguide 106 and isejected by grating 108. Grating 108 expands the pupil in a direction(e.g., vertically) different than the direction that light pipe 104expands the pupil in some embodiments.

In some embodiments, grating 108 expands the pupil vertically whilelight pipe 104 expands the pupil horizontally. Light pipe 104 can bedisposed as a horizontal beam expander, and waveguide 106 can bedisposed as a vertical beam expander and combiner in some embodiments.Light pipe 104 can be disposed as the vertical beam expander, andwaveguide 106 can be disposed as the horizontal beam expander andcombiner in some embodiments. In some embodiments, the display system100 provides additional field of view by implementing additional layersof light pipe 104 and waveguide 106.

Projector 102 provides the image with a single color of light ormultiple colors of light to light pipe 104. Projector 102 is acollimating projector, such as, a catadioptric collimating system.Projector 102 is comprised of multiple optical components integrated toprovide a compact package in some embodiments. Projector 102 isphysically attached to light pipe 104 and provides near collimated orcollimated P-type or S-type polarized light in some embodiments. In someembodiments, an air gap exists between projector 102 and light pipe 104.

Light pipe 104 is a tube, waveguide or other optical assembly thatallows light to travel from a first location to a second location insome embodiments. Light pipe 104 is an optical component that allowslight to gradually leak into waveguide 106 as light travels within lightpipe 104 in some embodiments. Advantageously, light pipe 104 does notadd significant haze or grating losses to the image provided by displaysystem 100 in some embodiments. Light pipe 104 captures the field ofview in three dimensions and guides the field of view along the lengthof light pipe 104 in some embodiments.

In some embodiments, light pipe 104 is a waveguide embodied as anelongated rectangular prism with a square or rectangular cross sectionalarea. Light travels through light pipe 104 in a corkscrew, spiral,helical, or other fashion where all four sides of the rectangularprismatic shape are struck by light as light travels from a first end toa second end. In some embodiments, light pipe 104 is made from opticalglass and includes a gradient reflection coating disposing an interfacebetween light pipe 104 and waveguide 106. In some embodiments, the lighttravels by total internal reflection on three sides of light pipe 104and by reflection off the gradient reflection coating on a fourth side.

In some embodiments, the gradient reflection coating is disposeddirectly on light pipe 104. Waveguide 106 receives light from thegradient reflective coating associated with light pipe 104. Light can beinput to an edge of waveguide 106 and can be output via grating 108.Grating 108 can be a holographic grating, a volume grating, a surfacerelief grating, or other output coupler. Grating 108 can provide pupilexpansion in a vertical direction while light pipe 104 provides pupilexpansion in a horizontal direction. Other directions for pupilexpansion are possible. Grating 108 can have a circular, oval,rectangular, or square shape.

With reference to FIG. 2A-C, a display system 200 includes a projector202, a light pipe 204 and a waveguide 206 and is similar to displaysystem 100 discussed with reference to FIG. 1. Projector 202, light pipe204 and waveguide 206 can be similar to projector 102, light pipe 104and waveguide 106, respectively, described above with reference toFIG. 1. Projector 202 is disposed to be worn at approximately an eyebrowlevel associated with a user 212. User 212 views the environment throughwaveguide 206 operating as a combiner where light is ejected from agrating 218 of waveguide 206 into the eye of user 212 in someembodiments. Although a monocular display system 200 is described below,display system 200 can be a binocular system in some embodiments. Lightpipe 204 is not required to be at a 90 degree angle with respect towaveguide 206 in some embodiments. Waveguide 206 can have a variety ofshapes including an irregular shape with a flat interface facing a sideof light pipe 204. Light pipe 204 can have a slanted orientationrelative to the eye of the user in some embodiments.

With reference to FIGS. 2B-C, projector 202 is a low cost projectorsystem in some embodiments. Projector 202 includes a mirror 222, beamsplitter 224, a lens 226, a beam splitter 228, a lens 230, a lightemitting diode source 232, and an image source 234. Projector 202 can beembodied as a catadioptric collimating system, such as a foldedcatadioptric projector.

Projector 202 can be implemented in any variety of fashions. Otherprojectors for some embodiments are discussed in U.S. application Ser.Nos. 13/251087, U.S. patent application Ser. No. 13/250,940, U.S. patentapplication Ser. No. 13/250,858, U.S. patent application Ser. No.13/250,970, U.S. patent application Ser. No. 13/250,994, and U.S. patentapplication Ser. No. 13/250,621. The components shown in FIGS. 2A-C arenot shown in a limiting fashion.

Lens 226 and 230 can be an assembly of lenses and can include a fieldflattening lens, collimating lenses, etc. Mirror 222 can be a powered,collimating mirror in some embodiments. Laser source 232 is a laserdiode or other device for providing laser light at a single wavelengththrough lens 230 in some embodiments. Laser source 232 can include aboard for a light emitting diode (LED). Beam splitter 228 reflects thelight from lens 230 to image source 234. Lens 230 can include a convexor spherical lens, polarizing film, retarder films, etc. Beam splitter228 is a polarizing beam splitter in some embodiments. An image fromimage source 234 is provided through beam splitter 228 to lens 226 insome embodiments. Lens 226 can include a convex lens, a polarizing film,and/or a retarder film in some embodiments. Image source 234 is a liquidcrystal display (LCD) or other image source in some embodiments.

Light received by lens 226 is provided to beam splitter 224. Beamsplitter 224 can be a polarizing beam splitter. Beam splitter providesthe light from lens 226 to mirror 222. Mirror 222 provides the lightthrough beam splitter 224 to light pipe 204 in some embodiments. In someembodiments, beam splitter 224 and mirror 222 are provided as anintegrated package attached to light pipe 204 and physically separatefrom lens 226.

Light pipe 204 includes an input coupler or input grating 242. Inputgrating 242 injects light from beam splitter 224 into light pipe 204.Light pipe 204 guides light to waveguide 206 which is ejected into theeye via grating 218. Input grating 242 is a reflection type gratingdisposed on an opposite side 244 of light pipe from a side 246 closestto beam splitter 224 in some embodiments. In some embodiments, inputgrating 242 is a transmission type grating on side 244 or embeddedwithin light pipe 204. In some embodiments, display system 200 iscompatible with dispersion compensation which allows use of LED andreduces the banding effect typically associated with lasers. Fordispersion compensation, the input and output gratings are “matched”(e.g., grating line orientations are either parallel to each other ormirror symmetric to each other (with respect to the interface facet),and that their surface pitches are identical) in some embodiments.

In some embodiments, light pipe 204 injects light into waveguide 206along its top edge. Alternatively, light can be ejected into an outsideor inside main surface of waveguide 206. In one embodiment, light pipe204 has a cross sectional area of five millimeters by five millimetersand a length of approximately 25 millimeters. In one embodiment,waveguide 206 touches light pipe 204 such that total internal reflectiondoes not occur on the bottom surface of light pipe 204.

With reference to FIGS. 3 and 4, a light pipe 400 can be utilized aslight pipe 104 or 204 described above with reference to FIGS. 1 and2A-C. Light pipe 400 includes an input grating 402, a beam splittingcoating 404, and an output coupler or a gradient reflection coating 406.Input grating 402 can be provided on a first side 421 of light pipe 400.First side 421 can correspond to a side closest to the user's eye insome embodiments. Alternatively, input grating 402 can be provided on aside 423 away from the user's eye.

Input grating 402 can be integral with light pipe 400 or can beexternally attached to light pipe 400. In some embodiments, inputgrating 402 is a surface relief grating having a period of approximately400 to 450 nanometers. Input grating 402 can be rotated to variousorientations depending upon system criteria and design parameters.Although shown at a first end 428 on a surface 421, input grating 402can be placed along any external surface of or within light pipe 400 atvarious locations. Input grating 402 can be a holographic grating, avolume grating, a surface relief grating, or other input coupler. Inputgrating 402 can be embedded, or embossed in some embodiments.

In some embodiments, light pipe 400 is optical glass (e.g., fusedsilica), plastic, or other material for transporting light. In someembodiments, light pipe 400 has neighboring sides at 90 degree angleswith respect to each other (e.g., square or rectangular in crosssection). The end of light pipe 400 can be coated with an absorptivematerial to reduce stray light in some embodiments. Beam splittingcoating 404 can be disposed in a middle of light pipe 400. In oneembodiment, light pipe 400 includes two plates with beam splittingcoating 404 disposed between the two plates. Beam splitting coating 404is parallel to a surface 434 and a surface 436. Beam splitting coating404 advantageously increases the number of rays propagating from inputcoupler 402 to reflection coating 406. Beam splitting coating 404 fillsin, bounces, and blends the image for uniformity in some embodiments.Beam splitting coating 404 can be manufactured from a metallic ordichroic optical coating.

Gradient reflection coating 406 can be a dichroic coating or a silvercoating covering surface 436 that gradually leaks light from light pipe400 into waveguide 106 or 206. Gradient reflection coating 406 isdisposed on surface of waveguide 106 or 206 associated with surface 436in some embodiments. Gradient reflection coating 406 provides very lowhaze and does not require a grating for ejection of light. Gradientreflection coating 406 is configured to leak light from light pipe 400to waveguide 106 or 206 such that the light is received with relativeuniformity and the pupil is expanded in some embodiments. In someembodiments, gradient reflection coating 406 is non-gradient reflectioncoating (e.g, a uniform reflection coating).

With reference to FIG. 5, light 412 entering light pipe 400 isdiffracted along a light path by input coupler 402 to travel along lightpipe 400. Light striking gradient reflection coating leaves light pipe400. In one embodiment, gradient reflection coating 406 is configured toleak about 15% of light into waveguide 106 or 206 embodied as a verticalbeam expander at an upper portion and gradually leaks a higherpercentage (up to 50%) producing uniform light output. Absorption bycoating 406 is preferably relatively low (e.g. less than 3%).

With reference to FIG. 6, a light pipe 604 includes an input grating 602and is attached to waveguide 606. Light pipe 604 and waveguide 606 canbe similar to light pipes 400, 204 and 104 and waveguides 206 and 106,respectively. A gradient reflection coating 610 is disposed in aninterface between light pipe 604 and waveguide 606. Light 612 travelsthrough light pipe 604 and is gradually released into waveguide 606. Insome embodiments, gradient reflection coating 610 is a half silvercoating of variable thickness. Gradient reflection coating 610 can bemonochromatic or polychromatic. In some embodiments, the facet of lightpipe 604 opposite to gradient interface coating 610 (the interface facetto waveguide 606) can be mirror-coated to reflect light even beyond atotal internal reflection condition to increase field of view.

With reference to FIG. 7, reflectance of p-polarized light is shown in agraph 700. Graph 700 includes a Y axis 904 showing reflectance inpercentage and an X axis 706 showing thickness of the coating innanometers. Graph 700 shows a number of lines indicating reflectance atparticular angles from 40 to 65 degrees. As shown, reflectance isrelatively uniform for a silver coating across varying angles.Accordingly, by controlling the thickness of gradient reflection coating610, an appropriate light output can be provided in some embodiments.

With reference to FIG. 8, a graph 800 shows reflectivity in percentageon Y axis 804 and the number of bounces in light pipe 604 on an X axis806. As shown in FIG. 8, the thickness of gradient reflective coating610 can be chosen according to line 804 to provide a uniform outputaccording to line 802 in some embodiments. The number of bounces inlight pipe 604 is correlated to a position in light pipe 604 along itselongated surface.

With reference to FIGS. 9 and 10, a light pipe and waveguide assembly1003 is disposed at a right angle 1005 with respect to projector 1002for display system 1000. Light pipe and waveguide assembly 1003 includeslight pipe 1004 and waveguide 1006 in some embodiments. Grating 1012 oflight pipe 1004 and grating 1014 of waveguide 1006 are disposedcompensate for angle 1005 in some embodiments. In some embodiments, theangles of orientation of gratings 1012 and 1014 match.

With reference to FIGS. 11 and 12, light pipe and waveguide assembly1005 is disposed at an acute angle 1015 with respect to projector 1002for display system 1000. Gratings 1022 and 1024 are oriented tocompensate for angle 1015. Gratings 1022 and 1024 can be disposed at asimilar angle. In some embodiments, the angles of orientation ofgratings 1022 and 1024 match.

With reference to FIGS. 13 and 14, light pipe and waveguide assembly1003 is disposed at an obtuse angle 1025 with respect to projector 1002for display system 1000. Grating 1032 in light pipe 1004 and grating1034 in waveguide 1006 are disposed to compensate for angle 1025 in someembodiments. In some embodiments, the angles of orientation of gratings1032 and 1034 match. Angles 1005, 1015 and 1025 can be used to provide amore compact design.

Different configurations of light pipes 104, 204 and waveguides 106 and206 are possible. Although edge coupled structures are shown, otherarrangements are possible. In some embodiments, the configurations areused in a sand wind and dust goggle or a frame for glasses. In someembodiments, the output gratings are displaced so that they line up withthe eye location in the goggle or the frame. In some embodiments, adisplay system uses more than one light pipe and waveguide to increasethe field of view. Such a display system can use a projector designed tooutput a higher field of view than a projector for single light pipewaveguide projectors (given its numerical aperture) in some embodiments.

The construction and arrangement of the systems and methods as shown inthe various exemplary embodiments are illustrative only. Although only afew embodiments have been described in detail in this disclosure, manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.). For example, the position of elements may bereversed or otherwise varied and the nature or number of discreteelements or positions may be altered or varied. Accordingly, all suchmodifications are intended to be included within the scope of thepresent disclosure. The order or sequence of any process or method stepsmay be varied or re-sequenced according to alternative embodiments.Other substitutions, modifications, changes, and omissions may be madein the design, operating conditions and arrangement of the exemplaryembodiments without departing from the scope of the present disclosure.

Although the figures may show a specific order of method steps, theorder of the steps may differ from what is depicted. Also two or moresteps may be performed concurrently or with partial concurrence. Suchvariation will depend on the software and hardware systems chosen and ondesigner choice. All such variations are within the scope of thedisclosure.

The construction and arrangement of the systems and methods as shown inthe various exemplary embodiments are illustrative only. Although only afew embodiments have been described in detail in this disclosure, manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.). For example, the position of elements may bereversed or otherwise varied and the nature or number of discreteelements or positions may be altered or varied. Accordingly, all suchmodifications are intended to be included within the scope of thepresent disclosure. The order or sequence of any process or method stepsmay be varied or re-sequenced according to alternative embodiments.Other substitutions, modifications, changes, and omissions may be madein the design, operating conditions and arrangement of the exemplaryembodiments without departing from the scope of the present disclosure.

Although the figures may show a specific order of method steps, theorder of the steps may differ from what is depicted. Also two or moresteps may be performed concurrently or with partial concurrence. Suchvariation will depend on the software and hardware systems chosen and ondesigner choice. All such variations are within the scope of thedisclosure.

What is claimed is:
 1. A near eye optical display, comprising: aprojector configured to provide an image; a light pipe comprising aplurality of elongated surfaces, the light pipe being configured toexpand the image in a first direction through one of the elongatedsurfaces, wherein light associated with the image travels through thelight pipe by striking three or more of the elongated surfaces; and awaveguide comprising an output grating, a first surface, a secondsurface, and a side surface, the first surface and the second surfacebeing an opposing surfaces, and having a larger area than the sidesurface, the output grating being configured to provide the imageexpanded in a second direction, the second direction being differentthan the first direction, wherein the image enters the waveguide fromthe one of the elongated surfaces of the light pipe.
 2. The near eyeoptical display of claim 1, wherein the first direction is orthogonal tothe second direction.
 3. The near eye optical display of claim 1,wherein the one elongated surface, the side surface, the first surfaceand the second surface are planar surfaces.
 4. The near eye opticaldisplay of claim 1, wherein the projector: is comprised of a displaysource comprising a collimating mirror, a pair of beam splitters, alight source, and a lens configured to provide the image as collimatedlight to the light pipe.
 5. The near eye optical display of claim 1,further comprising: a gradient reflective coating disposed on the oneelongated surface.
 6. The near eye optical display of claim 5, furthercomprising a beam splitting coating between an input coupler on thelight pipe and the gradient reflective coating.
 7. The near eye opticaldisplay of claim 6, wherein the input coupler is a volume hologram or asurface relief grating.
 8. The near eye optical display of claim 1,wherein the light pipe is disposed at an angle less than 90 degrees andgreater than 0 degrees between the one elongated surface and the firstsurface.
 9. The near eye optical display of claim 8, wherein an inputcoupler associated with the light pipe and the output grating aredisposed to compensate for the angle to the side surface.
 10. The neareye optical display of claim 9, wherein angle orientations for theoutput grating and the input grating match.
 11. A method of displayinginformation, the method comprising: receiving light in a light pipehaving at least four elongated surfaces, the light striking the fourelongated surfaces and traveling at least partially by total internalreflection within the light pipe; receiving the light from one of the atleast four elongated surfaces in a waveguide having a first surface anda second surface; providing the light to an output grating via totalinternal reflection between the first surface and the second surface;and providing the light from the waveguide via the output grating, wherethe light is provided with dual axis pupil expansion with respect to thelight received in the light pipe.
 12. The method of claim 11, whereinthe output grating is a volume hologram or surface relief grating. 13.The method of claim 11, further comprising beam splitting the lightreceived in the light pipe before the light enters the waveguide. 14.The method of claim 11, wherein the light pipe includes an inputcoupler.
 15. The method of claim 14, wherein the input coupler is asurface relief grating.
 16. An apparatus for providing an image, theapparatus comprising: a light pipe comprising at least four elongatedsurfaces, each elongated surface connecting to at least two other of theelongated surfaces, the light pipe being configured such that lightassociated with an image strikes the at least four elongated surfaces asthe light travels in a corkscrew or helical fashion within the lightpipe; and a waveguide comprising an input surface and an output surface,wherein the light from the light pipe is received at the input surfaceand the light is ejected from the output surface of the waveguide by anoutput grating.
 17. The apparatus of claim 16, wherein the apparatusprovides dual axis pupil expansion.
 18. The apparatus of claim 16,wherein the light pipe comprises an input grating.
 19. The apparatus ofclaim 16, further comprising a first beam splitting coating disposed inthe waveguide and a second beam splitting coating disposed in the lightpipe.
 20. The apparatus of claim 16, wherein the light pipe has arectangular prismatic shape.